North Dakota pulled within 63-61 with 17.7 seconds to play. Montana's Fabijan Krslovic forced a turnover, and the Grizzlies then made two free throws to seal it.
Gregory and Breunig each shot 50 percent from the floor for the Grizzlies (13-10, 9-3 Big Sky), who have won eight of their last ten games. Montana is in sole possession of third place in the conference, following Eastern Washington (19-5, 10-1) and Sacramento State (16-7, 10-2).
North Dakota's Quinton Hooker hit his second 3-pointer to pull within 61-58 with less than two minutes to play, but North Dakota couldn't push through on its way to its second straight loss.
Jaron Nash scored 19 points on 9-of-13 shooting, and grabbed nine rebounds to lead North Dakota (8-15, 4-8).